1) Field of the Invention
The present invention relates to crystallized glass articles having surface patterns imparting to them an appearance such as granite, marble or other natural stones which are adaptable for use as heat resistant, incombustible ornamental wall materials for buildings and the like, and in particular, to such crystallized glass articles having a surface pattern of a desired color or colors.
2) Description of the Prior Art
As substitution of natural marble for ornamental building materials, crystallized glass articles have been proposed which have high mechanical strength, excellent heat resistance and excellent efflorescence resistance.
U.S. Pat. No. 3,761,235 (Reference 1) discloses crystallized glass articles having marble-like appearance. The crystallized glass article is produced by heat-treating a crystallizable CaO-Al.sub.2 O.sub.3 SiO.sub.2 glass, which consists essentially of 15-40 wt % of CaO, 3-35 wt % of Al.sub.2 O.sub.3 and 40-75 wt % of SiO.sub.2.
U.S. Pat. No. 3,964,917 (Reference 2) discloses another crystallized glass article which is also provided with marble-like appearance. The crystallized glass is produced by heat treating a crystallizable CaO-Al.sub.2 O.sub.3 -SiO.sub.2 -ZnO glass consists essentially of 15-25 wt % of CaO, 3-13 wt % of Al.sub.2 O.sub.3, 50-65 wt % of SiO.sub.2 glass and 2-10 wt % of ZnO.
Japanese Patent Publication (JP,B2) No. 60-49145 (Reference 3) also discloses another crystallized glass article which consists essentially of 40-59% of SiO.sub.2, 15-25% of Al.sub.2 O.sub.3, 0-12% of MgO, 0-12% of ZnO, 1-5% of TiO.sub.2, 2-10% of B.sub.2 O.sub.3, 4-13% of Na.sub.2 O, 0-3% of ZrO.sub.2, 0-5% of K.sub.2 O, 0-5% of CaO, 0-5% of BaO, 0-1% of As.sub.2 O.sub.3, and 0-1% of Sb.sub.2 O.sub.3 based on the percentage by weight.
The above-described crystallized glass articles can be colored by addition of a coloring agent. However, it is difficult to make a desired surface color pattern of different colors.
U.S. Pat. No. 3,955,989 (Reference 4) discloses a crystallized glass article having a surface pattern like granite, marble or other natural stones which is formed by heat-treatment of collected small crystallizable glass masses. Each of the small masses precipitates needle-like .beta.-wollastonite crystals by the heat-treatment which extend from the surface of the small mass into the interior in a direction generally perpendicular to the surface of the small mass to thereby produce the surface pattern defined by the small masses forming the surface layer. Reference 4 also discloses a crystallized glass article having a colored pattern by spraying or applying a solution containing coloring ions onto the collected small masses prior to the heat-treatment. The coloring ions diffuse into the small masses so that the article is colored. However, the article has only a light color. That is, it is impossible to produce an article having a bright colored or a high contrast colored pattern.
JPA 63-40736 (Reference 5) discloses a method for producing a crystallized glass article with a colored pattern by mixing a crystallizable CaO-Al.sub.2 O.sub.3 -SiO.sub.2 glass powder and another crystallizable glass powder of CaO-Al.sub.2 O.sub.3 -SiO.sub.2 glass containing a coloring agent to form a mixture, then compacting the mixture to form a compact of a desired shape and heating the compact. However, it is difficult by the method to produce a large article because the compact is readily destroyed.